The invention relates to a linear guide arrangement with an elongated guide rail and a guide carriage that can travel thereon in lengthwise direction of the guide rail, in which a surface of the guide rail facing the guide carriage is covered by means of a cover band and in which, furthermore, a band securing element is placed in the vicinity of each of the two longitudinal ends of the guide rail.
The guide rails of such types of linear guide arrangements are normally fastened by means of screws to a main modular unit, for example, a linear guide casing or a mounting table. The fastening screwsxe2x80x94as seen from the surface facing the guide carriagexe2x80x94are inserted in bore holes of the guide rail. In order to rule out the obstruction in the movement of the guide carriage as a result of these bore holes, as well as to avoid contaminating the interior space of the carriage due to dirt accumulation on the guide rail, and particularly in the fastening bore holes, the holes are covered with a cover band. In order to protect the operating personnel from injury, on the one hand, and to ensure a secure hold of the cover band on the guide rail, on the other hand, in particular to prevent an axial shifting of the cover band, i.e., a shifting in the lengthwise direction of the guide rails, band securing elements, for example in the form of covering caps, are provided on both ends of the guide rail. The caps cover the band ends and are screwed down frontally with the guide rail. Reference is made in this regard to the brochure xe2x80x9cSTAR Ball Rail Systemsxe2x80x9d of the assignee of the present application, with Identification Number xe2x80x9cRD 82 201/07.99.xe2x80x9d The band securing elements known from DE 38 12 505 A1 are also screwed down with the guide rail.
The above-discussed screw connection of the band securing element with the guide rail raises difficulties, particularly in the so-called xe2x80x9cminiature guide rails,xe2x80x9d whose cross-sectional area can have values of less than 10 mmxc3x9710 mm. These guide rails are normally made of a completely hardened material so that the necessary, front-end thread bore hole must be placed in the hard material. This means costly production.
But even for guide rails with larger cross-sectional area, for which only the areas of the tracks for the rolling elements of the rolling element circuits of the guide carriage are normally hardened, putting in the thread bore hole necessary for the screwed connection between the band securing elements and the guide rail is an additional processing step to be executed on the guide rail, which is quite awkward to handle because of its length.
Reference is also made to U.S. Pat. No 5,297,873, JP-A-62-255612 and JP-A-2-300517 for the state of the art. These three publications all deal with guide rails without cover band and, in particular, with stoppers, which are used to limit the track of the guide carriage on the guide rail.
In comparison with the prior art, it is the object of the invention to specify for a linear guide arrangement of the type mentioned at the start band securing elements for the cover band of the guide rail, which ensure a secure fastening of the band end to the guide rail without requiring costly processing operations on the rail. This object, previously unknown from prior art, is solved according to a first aspect of the invention through a linear guide arrangement with an elongated guide rail and a guide carriage that can travel thereon in lengthwise direction of the guide railxe2x80x94wherein a surface of the guide rail facing the guide carriage is covered by means of a cover band, a band securing element is placed in the vicinity of each longitudinal end of the guide rail, which two band securing elements jointly secure the cover band to the guide rail at least with respect to its displacement in the lengthwise direction of the guide rail, and each of the band securing elements at least impedes a movement of the cover band relative to the guide rail, with such movement to be directed to the other band securing element.
While in the linear guide arrangements of the prior art, the band securing elements screwed on with the guide rail served as stoppers for the cover band, wherein each of these band securing elements prevented axial movement of the cover band beyond the longitudinal end of the guide rail, to which the respective band securing element is also fastened, an entirely different solution is now provided according to the invention. According to the invention, each of the band securing elements prevents axial movement of the cover band beyond the longitudinal end of the guide rail on which the other band securing element is arranged.
This is made possible by a positive-fitting interactive connection between the band securing element and the cover band as well as a non-positive engagement between the band securing element and the guide rail or a positive-fitting engagement of a stopping face of the band securing element with a counter stopping face of the guide rail. As a result, a screw connection between the band securing element and the guide rail can be dispensed with.
The positive-fitting interactive connection between the band securing element and the cover band may be prepared, for example, by providing at least one projection on one of the parts, i.e., the band securing element or the cover band, which engages in a corresponding recess provided on the other part, i.e., the cover band, or the band securing element.
In order to modify the previous production of the cover band as little as possible, it is suggested that the cover band, preferably roughly in its transverse center, exhibit at least a recess into which a projection of the band securing element can engage in a direction essentially orthogonal to the band plane. In such case, the cover band already conventionally used need only be subjected to a further processing step, for example, drilling, punching, or the like, in order to form the recess in it.
The projection mentioned may be integrally formed in one piece on the band securing element. It is nevertheless likewise basically possible for the projection to be made separately from a base part of the band securing element, for example, as an engaging or connecting pin.
Alternatively to the preferably centrally-located recess, the cover band may nevertheless also have at least a recess at the side, into which a projection of the band securing element engages essentially crosswise to the cover band. In both embodiments, the projection can be connected with the band securing element through a flexible web, so that it can engage in a snapping manner in the recess of the cover band to produce the interactive contact between the band securing element and the cover band. In this case, the snap connection may advantageously be designed as a detachable snap connector.
To provide the previously mentioned non-positive engagement of the band securing element and the guide rail, at least a clamping projection may be provided on the band securing element. This clamping projection may engage at the side of the guide rail, for example, preferably engaging in longitudinal grooves provided in the side faces of the guide rail in which the tracks for the rolling elements of the rolling element circuits of the guide carriage are formed. At least two such clamping projections are preferably formed on the band securing element, with the clamping projections being arranged on both sides of the guide rail. This can increase the clamping effect on the guide rail held between these clamping projections and, consequently, the hold of the band securing element on the guide rail.
To provide the previously mentioned positive-fitting engagement of the band securing element and the guide rail, which is active at least with respect to a movement of the band securing element under consideration, to be directed to the other band securing element, the band securing element under consideration may have a flange extending essentially orthogonal to the lengthwise direction of the guide rail, with the flange facing or adjacent to a frontal area of the guide rail in the installed state of the linear guide arrangement. Since the entire frontal area of the guide rail is available as a stopping face on the side of the guide rail, and also the stopping face of the flange can be formed in a corresponding size on the sides of the band securing element, the forces to be transferred are distributed over a relatively large area, which reduces the risk of damage, particularly to the band securing element, due to the accompanying pressure reduction.
The fact that space must in any event be provided for the flange on the front end of the guide rail can be used to place also the positive-fitting connection between cover band and band securing element in this area. To this end, the cover band, for example, may exhibit a length greater than the guide rail and the cover band may be connected in a positive-fitting manner with the band securing element in a section projecting over the guide rail. In particular, when using a retention pin, which engages in a positive-fitting manner in a recess of the cover band, the forces introduced by the cover band to this pin may be passed on to the band securing element over a relatively large surface, which in turn reduces the risk of damage. The retention pin may be formed from a stud, for example.
For secure guiding of the cover band, it is suggested that the band securing element be provided with a cavity, preferably a passage, into which the section of the cover band projecting over the guide rail can be introduced. The band securing element can be made of at least two parts, with one part exhibiting an upper terminating faces and the other part exhibiting a lower terminating faces of the cavity or of the passage, and preferably with the two side terminating faces of the cavity or of the passage being formed on one and the same part. The two parts at least can be secured to one another preferably through snapping connectors. A separate retention pin may be provided as another part of the band securing element. However, it is also possible to design the retention pin as one piece with one of the two parts.
To simplify its production, the band securing element may be made at least partially as a plastic or metal injection molded part.
According to an independent, second aspect of the invention, the desired securing of the cover band to the guide rail without the use of screw connections can also be achieved through a linear guide arrangement with an elongated guide rail and a guide carriage that can travel thereon in lengthwise direction of the guide rail, wherein a surface of the guide rail facing the guide carriage is covered by means of a cover band, wherein, furthermore, in the vicinity of at least one of the two longitudinal ends of the guide rail, a band securing element is placed, and wherein at least one of the band securing elements engages in a non-positive manner with the cover band as well as with the guide rail.
Through the non-positive engagement of the band securing element with the guide rail, the non-positive engagement of the band securing element with the cover band is also ensured, in the course of which a direct, non-positive engagement is simultaneously preferably brought about between the cover band and the guide rail. This can be achieved by designing the band securing element as a clamp strap element, for example. This clamp strap element may exhibit two free ends that engage at the side of the guide rail, each preferably engaging in a longitudinal groove of the guide rail. In turn, at least one track for the rolling elements of a rolling element circuit of the guide carriage can be designed in this longitudinal groove.
To produce the desired non-positive connections, the clamp strap element may press the cover band against the guide rail in a section (middle section) placed between its two free ends. It should be stressed that the term xe2x80x9cmiddle sectionxe2x80x9d need not necessarily mean the geometric center between the two free ends of the clamp strap element. Rather, the pressure site can also be provided in a section more to the side of the clamp strap element, provided only that these are placed between the two free ends of the clamp strap element.
The clamp strap element may have a clamp strap made up of one or several pieces, preferably manufactured from an elastic material, such as metal or synthetic material. To achieve the non-positive engagement with the cover band, the clamp strap or at least one clamp strap part in the vicinity of the middle section of the clamp strap element can be made with a bulge, preferably designed in the form of a bead.
In order to reliably ensure the desired non-positive connection, the clamp strap element may additionally include a clamping device, by means of which the pressing force of the clamp strap element against the cover band can be adjusted.
In accordance with the first variation of the embodiment, the clamping device may include a device for changing the distance or spacing between the first section of the clamp strap and the second section of the clamp strap adjacent to a free end of the clamp strap and preferably running essentially parallel hereto. The distance-changing device may be a stud, for example, which penetrates openings of the two sections of the clamp strap, whereby the opening of the section of the clamp strap away from the head of the stud is provided with an internal screw thread that has a combined effect with the screw thread on the stud shaft, while the size of the opening of the section adjacent to the head of the stud is sufficiently large that the shaft of the stud provided with the screw thread can penetrate it without any interaction therewith.
In a multi-piece construction of the clamp strap, it can be provided in a corresponding manner for the clamping device to include a device for changing the distance between a first clamp strap part and a second clamp strap part adjacent to a free end of the clamp strap, preferably running essentially parallel thereto.
The middle section of the clamp strap element may be provided on either of the clamp strap parts. If it is provided on the first clamp strap part, the second clamp strap part on a side of the first clamp strap part facing away from the cover band may support itself on this middle section. The desired non-positive engagement between the clamp strap element and the cover band may then be achieved when the second clamp strap part supports itself on the first clamp strap part in the middle section of the clamp strap element, as well as when the second clamp strap part supports itself on a section of the first clamp strap part which connects to the middle section on the side opposite the free end of the first clamp strap part.
According to a second variation of the embodiment, the clamping device may include a clamping element which forms one of the free ends of the clamp strap element. Also in this case, the clamping element may be made of a straining screw, which is threadably engaged with the clamp strap or at least one clamp strap part.
According to a first sub-variation of this second variation of the embodiment, the straining screw may have a conically shaped head and a screw axis running preferably orthogonal to the cover band plane, with the screw axis engaging with the cone surface in a longitudinal groove at the side of the guide rail. By screwing the straining screw into the clamp strap or the appropriate clamp strap part, the desired non-positive engagement of the clamp strap element and the cover band, i.e., the desired clamping effect between these two parts, is achieved.
In a second sub-variation, the straining screw may exhibit a conically shaped tip and a screw axis preferably running essentially crosswise to the cover band, the screw axis being adjacent with the cone surface to an edge of a longitudinal groove at the side of the guide rail. When the straining screw is screwed into the clamp strap or the corresponding clamp strap part, the screw axis wanders away from the cover band plane, which in turn produces or intensifies the desired non-positive engagement between the clamp strap element and the cover band.
According to a third sub-variation, the straining screw can eventually engage the guide rail at the side, wherein its screw axis runs at least partially in a direction essentially orthogonal to the cover band plane. As a result of the slanting course of the screw axis at least to the cover band plane, the desired non-positive strength between the clamp strap element and the cover band is in turn produced or intensified when the straining screw is screwed into the clamp strap or into the corresponding clamp strap part.
According to a further alternative variation of the embodiment, the clamping device may also exhibit a cam which is rotatably arranged around an axis on the clamp strap element, preferably in its middle section, and the peripheral surface of which can be pressed on the cover band.
Finally, according to a further variation of the embodiment, the clamp strap can also exhibit a greater orthogonal spacing from the cover band in the vicinity of one side edge of the cover band than in the vicinity of the other side edge, and the clamping device can include a spline that can be displaced in crosswise direction of the cover band.
In all the above-discussed embodiments, the hold at the side of the cover band relative to the guide rail can be ensured by the cover band being snapped on the guide rail with its side edges.
Finally, the non-positive engagement between the clamp strap element and the cover band can also be achieved if the clamping device, for example the straining screw, presses on the side against one of the side edges of the cover band. In this case, the straining screw in turn preferably forms one of the free ends of the clamp strap element. As a result of pressing on the side edge of the cover band, the straining screw draws the other free end of the clamp strap element into a lateral arrangement against the guide rail or, in a side engagement, into a longitudinal groove of the guide rail.